Hematology and Oncology Pharmacology Flashcards
heparin–mechanism
lowers the activity of thrombin and factor Xa
short half life
heparin–use
immediate anticoagulation for pulmonary embolism (PE), acute coronary syndrome, MI, deep vein thrombosis (DVT),
used during pregnancy–does not cross placenta
follow PTT
heparin–toxicity
bleeding
thrombocytopenia (HIT)
osteoporosis
drug-drug interactions
heparin–antidote
use protamine sulfate–positively charged mc that binds negatively to heparin
what are the advantages/disadvantages to using low molecular weight heparins?
low molecular weight heparins–enoxaparin, dalteparin
advantages:
act more on factor Xa
have better bioavailability
2-4 times longer half life
can be administered subcutaneously and w/o lab monitoring
disadvantage:
not easily reversible
explain heparin induced thrombocytopenia (HIT)
development of IgG antibodies against heparin bound platelet factor 4 (PF4)
antibody heparin PF4 complex activates platelets –> thrombosis and thrombocytopenia
name the direct thrombin inhibitor
bivalirudin–related to hirudin, the anticoagulant used by leeches
direct thrombin inhibitor–mechanism
directly inhibits activity of free and clot-associated thrombin
direct thrombin inhibitor–use
venous thromboembolism
atrial fibrillation
can be used in HIT
doe not require lab monitoring
direct thrombin inhibitors–toxicity
bleeding
antidote for direct thrombin inhibitors
no specific reversal agent
can attempt to use activated prothrombin complex concentrates (PCC) and/or fibrinolytics (eg. transexamic acid)
warfarin–mechanism
interferes with gamma carboxylation of vitamin K dependent clotting factors II, VII, IX, X, and proteins C and S
metabolism affected by polymorphisms in the gene for vitamin K epoxide reductase complex (VKORCI)
in lab–effect on EXtrinsic pathway and inc PT, long half life
“the EX-President went to WAR(farin).”
warfarin–use
chronic anticoagulation–venous thromboembolism prophylaxis and prevention of stroke in atrial fibrillation
follow PT/INR
can warfarin be used in pregnant women? why?
no, b/c crosses placenta (unlike heparin)
warfarin–toxicity
- bleeding
- teratogenic
- skin/tissue necrosis
- drug-drug interactions
- proteins C and S have shorter half lives than clotting factors II, VII, IX, X which results in early transient hypercoagulability with warfarin use
- skin/tissue necrosis within first few days of large doses believed to be due ot small vessel microthromboses
antidote for warfarin
vitamin K
how would you rapidly reverse warfarin?
fresh frozen plasma
explain heparin “bridging”
- heparin frequently used when starting warfarin
- heparin’s activation of antithrombin enables anticoagulation during initial, transient hypercoagulable state caused by warfarin
- initial heparin therapy reduces risk of recurrent venous thromboembolism and skin/tissue necrosis
compare and contrast heparin vs. warfarin
name direct factor Xa inhibitors
ApiXaban
rivatoXaban
direct factor Xa inhibitors–mechanism
bind to and directly inhibit factor Xa
direct factor Xa inhibitors–use
- treatment and prophylaxis for DVT and PE (rivaroxaban)
- prophylaxis in patients with atrial fibrillation
- oral agents do not require coagulation monitoring
direct factor Xa inhibitors–toxicity
bleeding–no reversal agent is available
name the thrombolytics
Alteplase (tPA)
Reteplase (rPA)
streptokinase
tenecteplase (TNK-tPA)
thrombolytics–mechanism
- directly or indirectly aid conversion of plasminogen to plasmin, which cleaves thrombin and fibrin clots
- inc PT
- inc PTT
- no change in platelet count
thrombolytics–use
- early MI
- early ischemic stroke
- direct thrombolysis of severe PE
thrombolytics–toxicity
- bleeding
when are thrombolytics contraindicated?
- patients with:
- active bleeding
- history of intracranial bleeding
- recent surgery
- known bleeding diatheses
- severe hypertension
how to treat toxicity of thrombolytics
- aminocaproic acid, an inhibiotr or fibrinolysis
- can also use fresh frozen plasma and cryoprecipitate to correct factor deficiencies
name the ADP receptor inhibitors
clopidogrel
prasugrel
ticagrelor (reversible)
ticlopidine
ADP receptor inhibitors–mechanism
- inhibit platelet aggregation by irreversibly blocking ADP receptors
- prevent expression of glycoproteins IIb/IIIa on platelet surface
ADP receptor inhibitors–use
- acute coronary syndrome
- coronary stenting
- decrease incidence or recurrence of thrombotic stroke
ADP receptor inhibitors–toxicity
- neutropenia (ticlopidine)
- TTP may be seen
cilostazol, dipyridamole–mechanism
- phosphodiesterase III inhibitor
- inc cAMP in platelets
- results in inhibition of platelet aggregation
- vasodilators
cilostazol, dipyridamole–use
- intermittent claudication
- coronary vasdilation
- prevention of stroke or TIAs (combined with aspirin)
- angina prophylaxis
cilostazol, dipyridamole–toxicity
- nausea
- headache
- facial flushing
- hypotension
- abdominal pain
name the glycoprotein IIb/IIIa inhibitors
- abciximab
- eptifibatide
- tirofiban
glycoprotein IIb/IIIa inhibitors–mechanism
- bind to the glycoprotein receptor IIb/IIIa on activated platelets
- prevent aggregation
what is abciximab made from?
(glycoprotein IIb/IIIa inhibitors)
monoclonal antibody Fab fragments
glycoprotein IIb/IIIa inhibitors–use
- unstable angina
- percutaneous transluminal coronary angioplasty
glycoprotein IIb/IIIa inhibitors–toxicity
- bleeding
- thrombocytopenia
what are the anti-metabolite drugs?
- azathiprine and 6-mercaptopurine
- cladribine
- cytarabine
- 5-fluorouracil
- methotrexate
azathiprine, 6-mercaptopurine–mechanism
- purine analogs –> dec de novo purine synthesis
- activated by HGPRT
- azathioprine is metabolized into 6-MP
azathiprine, 6-mercaptopurine–use
- prevent organ rejection
- rheumatoid arthritis
- IBD
SLE - used to wean patients off steroids in chronic dz and to treat steroid refractory chronic disease
azathiprine, 6-mercaptopurine–toxicity
- myelosuppression
- GI
- liver
how are azathiprine and 6-mercaptopurine metabolized, and how does this affect toxicity?
- they are metabolized by xanthine oxidase
- so, they have inc toxicity with allopurinol or febuxostat
cladribine–mechanism
- purine analog
- multiple mechanisms–inhibition of DNA polymerase, DNA strand breaks
cladribine–use
- hairy cell leukemia
cladribine–toxicity
- myelosuppression
- nephrotoxicity
- neurotoxicity
cytarabine (arabinofuranosyl cytidine)–mechanism
- pyrimidine analog
- inhibition of DNA polymerase
cytarabine (arabinofuranosyl cytidine)–use
- leukemias (AML)
- lymphomase
cytarabine (arabinofuranosyl cytidine)–toxicity
- myelosuppression with megaloblastic anemia
- CYTarabine causes panCYTopenia